Ok, just to take a step back and address the original issue, how to read the spectral analysis charts. The most important thing to remember is that white light contains ALL wavelengths of visible light. What is being shown in those graphs is how much of each wavelength is present in the light source. There are no equations or formulas to come to this conclusion, these are independent pieces of data that rely on no other factors and can be measured with the correct instrument. The curve of the cart is the intensity of each independent wavelength at the given distance from the light source. Ultimately you are just looking at how warm or cool your shade of white light is. In terms of standard incandescent bulbs it is warm white vs. soft white; warm white being in the 2,500 - 3,500 Kelvin range and cool white being in the 4,000 - 6,500 Kelvin range. What I find usually helps people is looking at the spectrum analysis of an HPS bulb versus a spectrum analysis of a LED unit. We all know that HPS throws out an orange light to our eyes, which means the light is deficient in blues predominantly, but still lacking in greens and reds too. There is a major peak in the 550-600nm wavelengths.
As was stated earlier the wavelengths we would want to see peaks in is 470nm (blue) and 660nm (far red) because those drive the major photosynthetic reactions within the plants. But as was discovered when the purple LED units were produced (using predominantly red and blue diodes) was that there was still something missing and the plants didn't grow as well. Once white diodes started to be placed into the units the production quality and quantity started to go back up; this is because the yellow, green and orange wavelengths are still utilized by the plants to run metabolic processes. Ultimately white light is always going to be the best option, just think about the sun which puts off true white light, that is the light that grows the best plants.
Yes if the intensity of the light is too weak the plants will not grow well, but if we get the right balance of spectrum and intensity we will grow plants to their greatest potential.